Memory Request / Grant Daemons in Virtual Nodes for Moving Subdivided Local Memory Space from Vn to Vn in Nodes of a Massively Parallel Computer System

1. A computer-executed method for regulating memory in a first node of a computer system having a plurality of nodes, each said node having a respective plurality of processors and a respective common physical nodal memory accessible only to processes executing on one or more of the respective processors within the node, the method comprising the steps of: configuring said first node as a plurality of virtual nodes for executing respective processes, each process executing in a respective said virtual node, each virtual node having a respective disjoint subset of the respective plurality of processors of said first node, each said disjoint subset containing at least one of said plurality of processors for executing processes in the respective virtual node, and a respective discrete non-overlapping subdivision of said common physical nodal memory for use by processes executing within the respective virtual node, wherein each process is unable to access nodal memory outside the respective subdivision of said common physical nodal memory of the virtual node in which the process is executing; sending a request on behalf of a user process executing within a first virtual node of said plurality of virtual nodes to dynamically enlarge the size of the subdivision of said common physical nodal memory of said first virtual node for use by the user process, said request being sent by a first memory regulating process executing in said first virtual node to a second memory regulating process executing in a second virtual node of said plurality of virtual nodes; responsive to sending said request, granting said request, said request being granted by said second memory regulating process; and responsive to granting said request, dynamically enlarging the size of said subdivision of said common physical nodal memory of said first virtual node during execution of said user process for use by the user process, said dynamically enlarging step being performed by said first memory regulating process.

2. The method for regulating memory in a first node of claim 1 , wherein said request includes an amount of additional memory requested and priority data associated with the request.

3. The method for regulating memory in a first node of claim 1 , wherein each said virtual node comprises a respective daemon for performing the steps of: (a) as a requesting virtual node, sending a request from the requesting virtual node to another virtual node, said request requesting that the subdivision of the requesting virtual node be enlarged, and (b) as a virtual node other than a requesting virtual node, granting a request received from a requesting virtual node requesting the subdivision of the requesting virtual node be enlarged.

4. The method for regulating memory in a first node of claim 1 , further comprising the step of: accessing a record of said memory subdivisions to determine whether available memory exists for granting said request, wherein said sending a request step is performed only if said accessing a record step determines that available memory exists for granting said request.

5. The method for regulating memory in a first node of claim 1 , further comprising the steps of: monitoring available unused memory in each respective said subdivision to determine whether a need exists for additional memory within the subdivision; and responsive to determining that a need exists for additional memory within the subdivision, performing said steps of sending a request, granting said request, and dynamically enlarging the size of the subdivision.

6. The method for regulating memory in a first node of claim 1 , wherein said step of configuring said first node as a plurality of virtual nodes for executing respective processes comprises configuring said common physical nodal memory as said plurality of discrete non-overlapping subdivisions and a discrete portion of unattached memory not included in any of said discrete non-overlapping subdivisions; and wherein said step of dynamically enlarging the size of said subdivision of said common physical nodal memory of said first virtual node comprises attaching at least a portion of said unattached memory to the subdivision of said common physical nodal memory of said first virtual node.

7. The method for regulating memory in a first node of claim 1 , wherein said step of dynamically enlarging the size of said subdivision during execution of a respective process causes said subdivision to be enlarged for the remaining duration of the user process.

8. The method for regulating memory in a first node of claim 7 , wherein a size of a memory subdivision which was dynamically enlarged by said dynamically enlarging step is restored to a default state after termination of a respective user process for which the subdivision was dynamically enlarged upon initialization of a user process subsequent to the respective user process for which the subdivision was dynamically enlarged.